Oil base well treating fluids thickened by block copolymers

Abstract

Oil based well treating fluids comprise liquid mixtures of aliphatic and aromatic hydrocarbons containing aromatic hydrocarbons, polymeric materials inclusive of at least one block copolymer and polymer crosslinking agents, with the kinds and amounts of those materials tailored to the properties of the wells and the well treatment designs.

What is claimed is: 
     
       1. An oil based well treating fluid, comprising: a liquid mixture of aliphatic and aromatic hydrocarbons containing (1) at least one dissolved or dispersed polymer of the group consisting of at least one arene/diene block copolymer and mixtures of at least one arene/diene block copolymer with one or more solution-compatible thermoplastic polymers, with said block copolymers having at least one elastomeric block portion and one or more thermoplastic block portions and (2) at least one free-radical-forming polymer crosslinking agent of the group consisting of alkyl peroxides, dialkyl peroxides, hydroperoxides, acyl peroxides and peroxy ketals capable of crosslinking at least one of said dissolved or dispersed polymers within the liquid mixture at a temperature between the surface temperature at the well side and the reservoir temperature; and   within said liquid mixture, kinds and amounts of aromatic hydrocarbons, polymeric materials and types and amounts of polymer crosslinking agents which are correlated relative to the reservoir temperature and the well treatment design so that (a) at surface locations, the viscosity of the liquid mixture is low enough for pumpability but high enough for a low fluid loss into the reservoir, rocks, and (b) when the temperature of the liquid mixture is increased, the viscosity is, or becomes, high enough to suspend solid particles and, (c) when the liquid is maintained at reservoir temperature for a selected time, the viscosity becomes low enough for an effective removal of the liquid.   
     
     
       2. The fluid of claim 1 in which at least a significant proportion of the solid particles which said liquid mixture is capable of suspending comprise fracture propping particles which are included within the mixture when it is flowed into the well. 
     
     
       3. The fluid of claim 1 in which said block copolymer comprises an SBS tripolymer of styrene and butadiene. 
     
     
       4. The fluid of claim 1 in which said liquid mixture contains both a block copolymer and a solution compatible polymer of a different type. 
     
     
       5. The fluid of claim 1 in which said crosslinking agent is an alkylhydroperoxide. 
     
     
       6. The fluid of claim 1 in which said crosslinking agent is a mixture containing at least two such agents that react at different temperatures. 
     
     
       7. A well treating process comprising: dissolving or dispersing within a liquid mixture of aliphatic and aromatic hydrocarbons (1) at least one polymeric material of the group consisting of arene/diene type block copolymers and mixtures of arene/diene block copolymers with one or more solution-compatible thermoplastic polymers, with said block copolymers containing at least one elastomeric block portion connected to at least one thermoplastic block portion and (2) at least one free-radical-forming polymer crosslinking agent of the group consisting of alkyl peroxides, dialkyl peroxides, hydroperoxides, acyl peroxides and peroxy ketal, capable of crosslinking at least one of said dissolved or dispersed polymeric materials within the liquid mixture at a temperature between the surface temperature at the well site and the reservoir temperature; and   arranging the aromatic hydrocarbon content of the liquid mixture and the kinds and amounts of said polymeric materials and polymer crosslinking agents in the liquid mixture relative to the temperature and well treating operation design so that, at a well site surface location, the liquid mixture is pumpable but capable of exhibiting low fluid loss against the reservoir formation, and, at a subsurface location, the viscosity of the liquid mixture is, or becomes, high enough to be capable of suspending solid particles but, when the liquid mixture is maintained for the well treatment-designed time at the reservoir temperature, decreases to a viscosity low enough for an easy removal of the injected liquid; and   flowing the so-arranged liquid mixture into the well and into contact with said reservoir formation.   
     
     
       8. The process of claim 7 in which fracture propping particles are suspended in at least a portion of the liquid mixture flowed into the well. 
     
     
       9. The process of claim 7 in which gravel packing particles are suspended in at least a portion of the liquid mixture flowed into the well. 
     
     
       10. The process of claim 7 in which said liquid mixture contains both a block copolymer and a solution compatible polymer of a different type. 
     
     
       11. The process of claim 7 in which said crosslinking agent is an alkylhydroperoxide. 
     
     
       12. The process of claim 7 in which said crosslinking agent is a mixture containing at least two such agents that react at different temperatures.